I am not saying Djokovic WILL break Federer's slam semifinal record but it is not unrealistic he can. Right now there is nobody outside the top 4 who has a hope of beating him in a big match. His durability seems to be no longer a problem as it used to be either. So it is possible he will break the record, it is far from certain, just that he definitely could.

Right now one lapse does not cost him a match before the semis. He can play a crap match and still get through until the semis of a slam right now, that seems clear. Only an injury or illness would. Whether that changes depends how much the field 5 ranked or lower improves or how soon he declines with age. Nadal is more vurnerable to an early upset as he easier for someone redlining to overpower than Djokovic.